1. Technical Field
The present invention relates to a method for producing a propylene-based resin composition, to a propylene-based resin composition produced by the method, and to an injection molded article comprising the composition. More particularly, the invention relates to a method for producing a propylene-based resin composition which is superior in balance between rigidity and impact resistance and from which a molded article with good appearance is produced, to a propylene-based resin composition produced by the method, and to an injection molded article comprising the composition.
2. Description of the Related Art
Propylene-based resins have conventionally been used as materials for automobiles because they are superior in rigidity and impact resistance.
For example, JP-A61-69848 discloses a polypropylene resin composition containing a polypropylene resin, a fibrous filler and talc as a polypropylene resin composition which is a material suitable for the automotive and electrical fields and which can afford molded articles which have high impact strength, high heat-resistant rigidity and good surface appearance and cause little warp and deformation. It also discloses that the polypropylene resin composition can be obtained by kneading the ingredients fully uniformly by, for example, a method comprising a combination of dry blending and melt blending, a multi-stage melt-blending method or a simple melt-blending method.
JP-A 5-279526 discloses a polyolefin resin composition comprising a polypropylene resin, a fibrous filler and talc, which is light weight while maintaining characteristics inherent to filled polyolefin, namely, rigidity, heat resistance and coefficient of linear expansion and which can be used suitably as a molding material of automotive interior components. It also discloses, as a method for producing the resin composition, a method comprising feeding a polypropylene resin and talc quantitatively into a twin screw extruder through a hopper, followed by melt-kneading the resin and talc, feeding a fibrous filler quantitatively to a downstream portion of the twin screw extruder, and subsequently kneading the resulting mixture. It also discloses a polyolefin resin composition resulting from addition of an elastomer to the aforesaid resin composition.
JP-A 10-36586 discloses a polypropylene resin composition comprising a polypropylene resin, an ethylene-α-olefin copolymer, talc and a fibrous inorganic filler, which is superior in both rigidity and impact resistance as well as in surface appearance, dimension accuracy and moldability and which can be used suitably for automotive interior or exterior components. It also discloses, as a method for producing the polypropylene resin composition, a method comprising feeding a polypropylene resin, an ethylene-α-olefin copolymer and talc quantitatively into a twin screw extruder through a hopper, followed by melt-kneading them, feeding a fibrous inorganic filler quantitatively to a downstream portion of the twin screw extruder, and subsequently kneading the resulting mixture.